1. Field of the Invention
This invention relates to a structure for mounting an operating knob in an air-conditioner for a vehicle. The structure is useful for adjusting the amount of outside or the inside air introduced into the passenger compartment of a vehicle.
2. Description of the Related Art
Generally, in an air-conditioner of the type mounted on a vehicle, a ventilation duct is mounted in instrument panel. An air port is provided at a downstream end of the ventilation duct. Outside air or inside air, as desired, is introduced into the passenger compartment of the vehicle through the air port. A shut-out damper is provided in the ventilation duct and movable between open and closed positions to allow or interrupt the introduction of the air. The shut-out damper is connected to an operating knob, which opens and closes the damper by rotational operation. The operating knob is mounted on the ventilation duct in the following manner.
As shown in FIG. 7, a boss 31 provided to the operating knob 30 is fitted on a shaft 33 projecting from an outer side surface of the ventilation duct 32 so as to cover the shaft 33. A tapping screw 34 passes through a washer 35 and the boss 31, and is threaded into the shaft 33. The tapping screw 34 cuts threads on an inner peripheral surface of a screw hole 33a in the shaft 33 so as to be fixedly secured to the shaft 33. With this construction, the operating knob 30 is supported on the shaft 33 to be rotatable about the shaft 33 and is unable to break away from the shaft 33.
In the above conventional mounting structure, however, the tapping screw 34, the washer 35 and the like are required for mounting the operating knob 30 on the ventilation duct 32. Further, the operation of passing the tapping screw 34 through the washer 35 and the boss 31, as well as the operation of threading the tapping screw 34 into the internally-threaded portion 33a in the shaft 33, is required. As a result, the processes, i.e., the time and labor, required for the mounting operation increase so as to increase the production cost and otherwise make the mounting operation troublesome.